GB2473610A

GB2473610A - Surgical introducing tool kit

Info

Publication number: GB2473610A
Application number: GB0916195A
Authority: GB
Inventors: Brian Paul Casey
Original assignee: Corin Ltd
Current assignee: Corin Ltd
Priority date: 2009-09-16
Filing date: 2009-09-16
Publication date: 2011-03-23
Also published as: GB0916195D0

Abstract

A surgical introducing tool kit, the kit comprising a non-compressible fluid source 100 connectable to a surgical introducing tool. The tool has a shaft 12, preferably with a handle 14, and a head 16 at the end remote from the handle. The head 16 comprises a cup holding element for releasably holding a prosthetic cup, the holding element including a seal and at least one fluid path extending through the head, preferably at least part way along the shaft 12. Connecting the non-compressible fluid source 100 to the fluid path for drawing through hydraulic fluid creates a vacuum for temporarily holding the prosthetic cup to the head of the tool. A non-return valve 60 may be provided in the fluid path connecting the tool to the non-compressible fluid source 100. The non-compressible fluid source 100 may comprise a syringe 80 containing the non-compressible fluid or the shaft 12 may include a reservoir of the fluid.

Description

SURGICAL INTRODUCING TOOL KIT

The present invention relates to an improved surgical introducing tool kit, particularly but not exclusively for the introduction of a prosthetic acetabular cup on to a patient's acetabulum.

It is known from US3859992 and FR2797180 to provide a surgical introducing tool for an acetabular cup which utilises vacuum to hold the cup to the tool.

However, a specific problem with these known arrangements, and also with most other kinds of acetabular cup introducing tools, is that a surgeon will typically tilt the tool in different directions, once the acetabular cup has been placed in the patient's acetabulum, to reposition the cup at the optimum angle. This tilting movement results in the cup breaking free from the tool due to the relative angular displacement of the longitudinal axis of the tool and the polar axis of the cup, especially when the introducers use a vacuum to hold the cup to the tool.

US2005/0203535 (Paramount Medical Instruments, L.L.C.) discloses the use of subatmospheric pressure to hold an acetabular cup onto an engaging head of a surgical introducing tool with no external suction source being required. A valveless and open port sealable by a finger allows for the subatmospheric pressure to be created and to be broken to thereby selectably release the cup from the engaging head. However, this does not always create a satisfactory vacuum to retain the cup on the head during alignment and impaction of the component into the acetabulum.

EP1698306 (Corin Limited) describes a head for a surgical introducing tool having a cup holding element and a retaining element positioned radially outwardly relative to the holding element and dimensioned to be a close fit with the acetabular cup. The cup is held to the head by a vacuum created by means of an airline linked to an air suction device attached to the tool. The retaining element serves to limit relative angular displacement of the head while the cup is held by the holding element. This tool has been found to work satisfactorily but excessive forces of leverage may still lead to dissociation of the cup from the holding element.

The present invention seeks to provide a solution to this problem.

According to a first aspect of the present invention, there is provided a surgical introducing tool kit, the kit comprising a non-compressible fluid source connectable to a surgical introducing tool, the tool having a shaft with a head at one end thereof, the head comprising a cup holding element for releasably holding a prosthetic cup, the holding element including a seal and at least one fluid path extending through the head, whereby connection of the non-compressible fluid source to the fluid path for drawing fluid therethrough creates a vacuum for temporarily holding the prosthetic cup to the head of the tool.

The surgical introducing tool kit according to the first aspect of the present invention is particularly suitable for the introduction of an acetabular cup to an acetabulum.

The shaft may incorporate a handle at one end thereof remote from the head.

The shaft and/or handle may be modularly connectable to the head, for example, being screwthreadingly engagable. The at least one fluid path extending through the head of the tool preferably extends at least part way through the shaft.

Any suitable biocompatible non-compressible fluid may be utilised in the kit for providing the hydraulic medium, but preferably the non-compressible fluid is water or, more preferably, saline.

Preferably, tubing connects the fluid path of the tool to the non-compressible fluid source. The tubing is preferably connected to an exit port provided at the end of the fluid path in the shaft of the introducing tool, preferably being connected by means of a nipple connector. Additionally, or alternatively, the non-compressible fluid source may be connected to the end of the fluid path located in the head of the introducing tool.

Preferably, the kit includes a non-return valve in the fluid passage connecting the tool to the non-compressible fluid source. The non-compressible fluid source preferably comprises a syringe containing the fluid.

At least part of the shaft or the handle may comprise a hollow reservoir for receiving a non-compressible fluid, the reservoir being in fluid communication with the fluid path of the shaft and/or head. A plunger may be provided for reciprocal movement within the reservoir thereby forming a syringe that is integral with the introducing tool. A suitable seal should be provided between the head of the plunger and the internal walls of the shaft defining the reservoir.

A conventional 0-ring seal having a circular cross-section may be provided between the holding element and the cup but, more preferably, a sealing ring having a substantially D-shaped cross-section is provided between the holding element and the cup.

The tool may be provided with at least one retaining element to further assist in preventing undesirable release of the cup from the holding element, the retaining element being positioned radially outwardly relative to the holding element and dimensioned to be a close fit with the cup, so that, in use, relative angular displacement of polar axes of the head and the cup is prevented or limited by the retaining element while the cup is held by the holding element, so as to prevent the cup from being accidentally released from the holding element.

According to a second aspect of the invention, there is provided a method of introducing a prosthetic cup to a cup-shaped joint socket, in particular an acetabular cup to an acetabulum, the method comprising the steps of charging a fluid path provided through a surgical introducing tool with a non-compressible fluid, placing a prosthetic cup on to a head of the surgical introducing tool, and withdrawing the non-compressible fluid from the fluid path to create a vacuum to retain the cup on the head.

The method may further comprise orientating the cup on to the acetabulum and releasing the vacuum from the head to release the cup.

Preferably, the method utilises a surgical introducing tool kit according to the first aspect of the present invention.

The invention will now be more particularly described by reference to the following Example which provides a comparative analysis between the prior art pneumatic based cup introducer method and the hydraulic based cup introducer method of the present invention, and with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic elevational view of a prior art surgical introducing tool for an acetabular cup; Figures 2a to 2d are schematic views of a surgical introducing tool kit according to an embodiment of the present invention, illustrating one method for the attachment and release of an acetabular cup; and Figures 3a to 3d are schematic views of a surgical introducing tool kit according to an embodiment of the present invention, illustrating an alternative method for the attachment and release of an acetabular cup.

Referring firstly to Figure 1, there is shown an example of a surgical introducing tool 10 according to the prior art, the tool comprising a shaft 12 having a handle 14 at one end and a head 16 at the other end. The shaft 12, in this case, is non-rectilinear, being cranked to promote simplified access to a patient's acetabulum during use, particularly during minimal access surgery. However, the shaft 12 may be rectilinear.

The head 16 includes a base plate 18, a hemispherical cup holding element 20 provided centrally on one major surface 18a of the base plate 18, and a plurality of retaining elements 22.

The cup holding element 20 is dimensioned to be a substantially complementary fit with an articulating inner surface of a known acetabular cup, albeit this need not be the case. A head air passage 28 passes centrally through the base plate 18 into the cup holding element 20. The head air passage 28, in the cup holding element 20, branches into three sub-passages 30 which open out on the surface of the cup holding element 20, at positions which are spaced from each other and which are generally remote from the base plate 18.

The cup holding element 20 also includes an 0-ring seal 32 which extends around the cup holding element 20 at a position adjacent to the equatorial diameter of the cup. The 0-ring seal 32 is thus located between the base plate 18 and openings 34 of the air sub-passages 30.

The base plate 18 is dimensioned to overlap the cup holding element 20, thereby providing a flange 36 which extends around the cup holding element 20. The retaining elements 22 project from the flange 36, in spaced relationship to both the cup holding element 20 and each other. Three retaining elements 22 are provided (only two being shown in Figure 1), and are spaced equiangularly around the cup holding element 20.

The retaining elements 22 project from the flange 36 in parallel with each other, and extend arcuately along the surface of the flange 36.

The head 16 is screwthreadingly engagable, or otherwise modularly connectable, at the base plate 18 with the end of the shaft 12 opposite the handle 14. This allows pre-operative and intra-operative changing of the head 16 to one of different dimensions, for example when a different size of acetabular cup is required. However, the head may be permanently connected to the shaft.

The shaft 12 includes an internal air passage 40 which extends partway along the longitudinal extent of the shaft 12. The shaft air passage 40 opens out at the end 42 of the shaft 12 opposite the handle 14, and exits through a side 44 of the shaft 12 partway between the ends. Opening 46 of the shaft air passage 40 in the end 42 of the shaft 12 is positioned to align with opening 48 of the head air passage 28 on the base plate 18 of the head 16. One or more seals (not shown) are provided which, when the head 16 is engaged with the shaft 12, enables the head-and shaft-air passages 28 and 40 to fluid-tightly communicate and thus form a continuous air passage through the tool 10.

Theexitoftheshaftairpassage40throughtheside44oftheshaft l2isviaa nipple connector 50 integrally formed on the shaft 12. The nipple connector 50 enables connection of a suction line from remote air suction device (not shown). The shaft 12 also includes a vent anangement 52 for the shaft air passage 40.

In use, and once the head 16 is attached to the shaft 12, an acetabular cup of suitable size is urged onto the cup holding element 20 and retaining elements 22 until its rim abuts the base plate 18. The cup holding element 20 is dimensioned so that the 0-ring seal 32 forms a fluid-tight interference fit on the articulating inner surface of the acetabular cup, and the retaining elements 22 are received as close or tolerance fits in respective openings or slots provided in the rim of the acetabular cup.

An air line of an air suction device is connected to the nipple connector 50 and a vacuum is generated in the space between the cup, the cup holding element 20, and the 0-ring seal 32. The acetabular cup is thus securely held by the introducing tool 10.

The acetabular cup is introduced into the patient's body and positioned by impaction in the acetabulum. Once located, the surgeon can move the handle 14 of the tool 10 in a reciprocating manner, in other words angularly displace the longitudinal axis of the tool, to position the cup at the optimum angle. During this tilting movement, and since the acetabular cup is now held securely in the patient's acetabulum, slight relative angular displacement of polar axis P1 of the head 16 and polar axis P2 of the cup occurs. This results in slight separation or tilting of the head 16 / base plate 18 from the cup. The retaining elements 22 of the head 16 consequently move in the openings or slots provided in the rim of the acetabular cup 26. Each retaining element 22, when titled due to the slight separation, will tend to bind on the interior surfaces of its respective rim slot, thus preventing excessive movement which would otherwise cause the fluid-tight seal generated by the 0-ring seal 32 to break. Breakage of the fluid-tight seal causes a loss of vacuum and the acetabular cup to be no longer securely gripped by the tool 10.

Once the surgeon is satisfied that the acetabular cup is securely located in the patient's acetabulum, the pivotable lever 60 on the shaft 12 is operated to lift the air-tight cap 56 and release the vacuum between the cup holding element 20 and the cup.

The tool 10 can then be easily removed from the cup.

Figures 2a to 2d of the accompanying drawings illustrate a modified surgical introducing tool kit according to one aspect the present invention wherein a hydraulic medium is utilised to create a pressure drop below atmospheric pressure in the fluid flow cavity to hold the cup in place on the head of the tool whilst it is positioned for impaction. Identical features to those already identified and discussed in relation to the prior art surgical introducing tool shown in Figure 1 are given the same reference numerals and only the differences will be discussed in detail. The introducing tool in the illustrated example again includes a handle 14 with a cranked shaft 12 and head 16 but it is to be appreciated that the tool may simply comprise a modularly connectable shaft and head. A fluid passage (not visible in drawings) extends from the head 16 through the cranked shaft to an outlet port 40. A nipple connector 50 attaches a piece of tubing 55 having a non-return valve 60 therein to provide a fluid-flow passage from the head to the tubing. A detachable syringe 80 is attached to the remote end of the tubing, when required.

In one embodiment of the present invention, the head 16 of the surgical introducing tool is placed into a source of non-compressible fluid 100, particularly saline solution, and the fluid is drawn in through the fluid-flow passage by means of a syringe 80 attached to the end of the tubing 55 to charge the tool with the non-compressible fluid. The non-return valve 60 prevents the exit of fluid from the tool and the syringe is removed and fluid expelled from the syringe. The syringe is then re-attached, and the head of the tool is placed on to an acetabular cup 26 (see Fig. 2b). The plunger of the syringe is then pulled back drawing saline solution through the fluid passage thereby reducing the pressure within the tool resulting in the cup being held on to the head of the tool (Fig. 2c). The non-return valve prevents any pressure increase.

This enables the surgeon to securely locate the cup in the patient's acetabulum. Once in the correct position, the tubing is removed from the shank of the tool to release the suction and thereby release the cup from the head of the tool (Fig. 2d).

Alternative methods may be used for the creation of the vacuum by means of the saline solution, such as that as illustrated in Figures 3a to 3d. A syringe 80 is filled with saline solution and then attached to the head 16 (distal end) of the surgical introducing tool (see Fig. 3a). The fluid-flow passage is charged with fluid and the non-return valve prevents loss of fluid from the tool upon removal of the syringe. Air/fluid is then discharged from the syringe and the syringe is attached to the tubing 55 at the other end of the cranked shaft. The head 16 of the tool is placed on to an acetabular cup 26 and the plunger of the syringe is pulled back to draw fluid from the passageway to create a vacuum within the system to tightly hold the cup in place (Fig. 3c). Once impaction is complete the tubing is removed to release the pressure and cup (Fig. 3d).

A further embodiment of the present invention provides an integral syringe within the shaft or handle of the surgical introducing tool. The handle is provided with an internal reservoir which may be connected to the fluid path of the head and shaft, and a plunger is provided within the reservoir for reciprocal movement therewithin. The plunger may have a head extending transversely across the reservoir with a shaft or rod extending therefrom beyond the periphery of the shaft to allow for operation of the plunger. A suitable seal is provided between the head of the plunger and the internal wall of the handle defining the reservoir. The non-compressible hydraulic medium is provided within the reservoir.

The use of a hydraulic medium has been found to provide a much better vacuum between the tool and acetabular cup thereby providing a better surgical introducing tool kit for the surgeon. This is demonstrated in the following example which provides a comparative analysis of pneumatic versus hydraulic based cup introducer methods.

Example: Comparative analysis of hydraulic versus pneumatic based cup introducer methods.

A test was carried out to determine the pull-off force required to un-seat an acetabular cup from a surgical introducing tool using a prior art pneumatic medium and a hydraulic medium according to the present invention, both with and without a non-return valve provided in the air/fluid line to prevent backflow of air/fluid through the system.

The following components were used during testing: 6Oml syringe with incremental holes on the plunger to hold pressure; Sealy hand pump with pressure gauge; Load cell with cup clamp adaptor (AEP Transducers. CM680); Corin Cormet Cup sample (Part No. 179.156B); Cormet Precision insert, fitted with standard 0-ring (Part No. 379.116); Cormet Precision introducer and plate (Part No. BL379.027); and Non-return valve (Legris Part No. 445-3111). Operating pressure 0.3-10 bar.

In each test, a load cell was clamped on to a bench vice and the readout set to record the peak pull-off force. The cup was connected to the cup clamp adaptor and fitted to the load cell. The syringe, pump and inserts were then assembled using PVC tubing and T-pieces, such that the pump's gauge was able to measure the pressure drop as air or water was displaced from the system. Each combination (pneumatic with and without a non-return valve and hydraulic with and without a non-return valve) was tested three times.

In each separate test configuration 60m1 of air or water was displaced from the system and the pressure drop below ambient atmospheric pressure (referred to as the "pressure drop" below) was measured using the pressure gauge and the peak pull-off value measured by pulling the introducer in an upward motion until the pressure seal was broken. Peak pull off force readings were then taken from the load cell and recorded.

The tables below illustrate the results of the tests: Test 1 -Pneumatic without non-return valve.

Displacement / ml Pressure Drop / mm Hg Pull off Force / N 420 53.74 420 88.55 420 71.29 Test 2 -Hydraulic without non-return valve.

Displacement / ml Pressure Drop / mm Hg Pull off Force / N 620 101.40 640 123.86 650 121.01 Test 3 -Pneumatic with non-return valve.

Displacement / ml Pressure Drop / mm Hg Pull off Force / N 480 28.80 480 55.60 480 55.60 Test 4 -Hydraulic with non-return valve.

Displacement / ml Pressure Drop / mm Hg Pull off Force / N 630 121.04 680 119.44 660 119.44 Performance comparison (mean pressure drop in mm Hg) Pneumatic Hydraulic Pneumatic with Hydraulic with non-non-return valve return valve 420 637 480 660 Performance comparison (mean pull-off values in N) Pneumatic Hydraulic Pneumatic with Hydraulic with non-non-return valve return valve 7120 115.42 46.67 119.97 The results demonstrated a 62% increase in mean pull off achieved with the use of a hydraulic system, which increased to 68% when a non-return valve is fitted.

Thus, there is a clear distinction in the performance levels between the prior art pneumatic system and the hydraulic system according to the present invention.

The inclusion of a non-return valve into the hydraulic system provided a slightly greater improvement. The value of the non-return valve lies in the ability to generate suction in theatre without the need to rely on a suction pump which can lead to a variation in performance. The valve employed in the above tests only allowed flow once the pressure exceeded 0.3 bar (225mmHg) which was not achieved until 30-40m1 had been displaced into the syringe. The use of a valve with a lower operating range may further improve the performance of the hydraulic system and the usefulness of this feature.

The tool kit according to the present invention may utilise a head having a standard 0-ring seal with a circular cross-section to provide a seal against the bearing surface of the cup. However, with the increased pressure provided by the hydraulic system, there is a tendancy for this type of seal to "flip-out" during use and release the vacuum. Therefore, in a preferred embodiment, a modified sealing ring is provided having a D-shaped cross-section with a substantial proportion of the ring housed within a cut-out of the cup holding element and the rounded profile of the ring protruding therefrom for a sealing contact with the acetabular cup. This arrangement of seal was found to prevent disengagement of the sealing ring during testing.

It is to be appreciated that the hydraulic system may be utilised in any surgical introducing tool where a vacuum is required to retain a prosthesis on a tool and is not limited to the acetabular cup introducing tool specifically described herein.

Furthermore, the specific example of a acetabular introducing tool described herein provides only one example of the type of acetabular introducing tool that may be used.

For example, it is to be appreciated that the tool may not include retaining elements or alternatively, any suitable number of retaining elements, and therefore corresponding recesses, may be provided. Only a single retaining element may be required. Although the retaining elements are described as being tongues, the retaining elements can be pins or any other suitably shaped projection. The or each opening, which includes a shoulder and a recess, when in the acetabular cup may be a slot, channel, or any close-or tolerance-fitting complementarily shaped opening.

It is possible that the rim of the acetabular cup can include one or more projections, instead of, or additionally to, the openings or slots. In this case, the retaining elements will be, or include, openings or slots formed in the flange or flanges of the base plate. These colTesponding openings or slots will be dimensioned to closely fit the or each projection on the cup.

The retaining element or elements of the head have a close or tolerance fit with the or each conesponding formation on or adjacent to the rim of the cup, in at least a radial direction of the cup holding element.

The cup holding element described above can be any shape that ensures that an adequate vacuum seal is formed between the element and the cup by the sealing ring.

Regardless of shape, the cup holding element will still inherently have a polar axis.

Although three air sub-passages are suggested in the cup holding element, any suitable number of passages, including a single sub-passage, can be utilised.

It is thus possible to provide a kit for a surgical introducing tool that more securely holds an acetabular cup during insertion.

Claims

CLAIMS1. A surgical introducing tool kit, the kit comprising a non-compressible fluid source connectable to a surgical introducing tool, the tool having a shaft with a head at one end thereof, the head comprising a cup holding element for releasably holding a prosthetic cup, the holding element including a seal and at least one fluid path extending through the head, whereby connection of the non-compressible fluid source to the fluid path for drawing fluid therethrough creates a vacuum for temporarily holding the prosthetic cup to the head of the tool.
2. A surgical introducing tool kit as claimed in claim 1 wherein the non-compressible fluid for providing a hydraulic medium is a biocompatiable liquid.
3. A surgical introducing tool kit as claimed in claim 2 wherein the non-compressible fluid is selected from water or saline.
4. A surgical introducing tool kit as claimed in claim 1, 2 or 3 wherein the shaft incorporates a handle at one end thereof remote from the head.
5. A surgical introducing tool kit as claimed in any one of the preceding claims wherein the at least one fluid path extends at least part way through the shaft.
6. A surgical introducing tool kit as claimed in claim 5 wherein the fluid path extending through the shaft terminates in an exit port.
7. A surgical introducing tool kit as claimed in claim 6 wherein tubing connects the exit port to the non-compressible fluid source.
8. A surgical introducing tool kit as claimed in any one of the preceding claims wherein the non-compressible fluid source is connectable to an end of the fluid path located in the head of the introducing tool.
9. A surgical introducing tool kit as claimed in any one of the preceding claims wherein a non-return valve is provided in the fluid path connecting the tool to the non-compressible fluid source.
10. A surgical introducing tool kit as claimed in any one of the preceding claims wherein the non-compressible fluid source comprises a syringe containing the non-compressible fluid.
11. A surgical introducing tool kit as claimed in any one of claims 1 to 4 wherein a syringe containing the non-compressible fluid is formed integrally within the shaft.
12. A surgical introducing tool kit as claimed in claim 11 wherein the shaft includes a reservoir for containing the non-compressible fluid, the reservoir being in fluid communication with the fluid path of the head and having a plunger for reciprocal movement through the reservoir.
13. A surgical introducing tool kit as claimed in any one of the preceding claims wherein the seal comprises an 0-ring seal having a circular cross-section.
14. A surgical introducing tool kit as claimed in any one of claims 1 to 12 wherein the seal comprises a sealing ring having a substantially D-shaped cross-section.
15. A method of introducing a prosthetic cup to a cup-shaped joint socket, in particular an acetabular cup to an acetabulurn, the method comprising the steps of charging a fluid path through a surgical introducing tool with a non-compressible fluid, placing a cup on to a head of the surgical introducing tool, withdrawing the non-compressible fluid from the fluid path to create a vacuum to retain the cup on the head.
16. A method according to claim 15 further comprising orientating the cup on to the joint socket and releasing the vacuum from the head to release the cup.